Stabilization of perchloroethylene with alkoxyalkylnitriles



United States Patent STABILIZATION 0F PERCHLOROETHYLENE WITHALKOXYALKYLNITRILES Application February 17, 1953, Serial No. 337,441

12 Claims. (Cl. 260652.5)

No Drawing.

This invention relates to the stabilization of perchloroethylene.

It is known that perchloroethylene has a tendency to decompose duringuse, storage, and shipment. This tendency is known to be more pronouncedwhen it is in contact with metallic surfaces, such as iron or copper.Such decomposition renders these compounds objectionable when they areemployed for certain commercial operations.

One of the important commercial uses of perchloroethylene is as asolvent, for example, in dry cleaning of wearing apparel, rugs, andother fabric materials. It is an excellent solvent for oils and greases.However, when it decomposes, the products of decomposition interfere tosuch an extent as to materially injure its beneficial effects. Whenemployed in metal structures, the problem of corrosion of the metalcaused by decomposition of perchloroethylene is quite serious.

Various chemical compounds have heretofore been proposed for use asstabilizers for halogenated aliphatic hydrocarbons andperchloroethylene. Among those which have been proposed are,benzaldehyde, cyclohexane, toluene, benzyl chloride, amylenehexylresorcinol, butyl mercaptan, ethyl acetate, guanidine, pyridine,and others. For certain purposes, these above stated compounds areunsatisfactory in that they are ineffective stabilizers forperchloroethylene, or their odor or color is objectionable.

In accordance with this invention, it has been discovered thatperchloroethylene is satisfactorily stabilized when a small stabilizingamount of an alkoxyalkylnitrile containing 1 to 3 carbon atoms in thealkoxy group and 1 to 3 carbon atoms in the alkyl group, such as 5-ethoxypropionitrile, is added thereto. Such stabilized compositions haveacceptable odor and color characteristics. These alkoxyalkylnitrileshave a boiling point not over about 200 C. They include, for example,S-ethoxypropionitrile, S-methoxypropionitrile,fl-isopropoxypropionitrile, fi-methoxyacetonitrile,fi-ethoxyacetonitrile, 5- isopropoxyacetonitrile, etc. These compoundsperform as satisfactory stabilizers even when the composition has beendistilled many times.

The amount of the alkoxyalkylnitrile stabilizer which is required tostabilize perchloroethylene is exceedingly small, about 0.01 to 0.1 percent by weight of alkoxyalkylnitrile being desirable to obtain optimumresults. However, larger amounts up to approximately 1 to 2 per cent areeflectivc and may be employed if economically feasible.Perchloroethylene so stabilized remains stable over many months evenafter repeated distillations.

The stabilizing effect of the alkoxyalkylnitriles on perchloroethylenehas been established, according to the invention, by means of a testconducted over a 72-hour period. The test is performed by refluxingperchloroethylene in a flask in the presence of water, strips of copper,and the stabilizer. One hundred milliliters of perchloroethylene isplaced in a 300-milliliter flask and 0.2 milliliter of water is added.The flask is attached to v a small Soxhlet extractor and a bulb typeAllihn con- ICC denser is attached to the extractor. One weighed copperstrip is placed in each of the flask, extractor, and condenser. Thecopper strip which is placed in the condenser is placed so that theperchloroethylene condenses on the strip. The condenser is connected toa water scrubber to absorb any HCl evolved during the test. Theperchloroethylene is heated to boiling point, the heating being carriedout so that the extractor empties at 8 to 10 minute intervals. Al00-watt incandescent bulb is placed one inch from the vapor line of theextractor to furnish energy for photochemical oxidation.

After the test is completed, part of the water in the scrubber is pouredthrough the condenser and extractor and finally into the flask. Thewater and perchloroethylene are poured into a beaker, phenolphthalein isadded, and the water layer is titrated with 0.01 N NaOH. The copperstrips are weighed to determine their weight loss during the test.

The following table shows the results of tests of variousalkoxyalkylnitrile stabilizers on perchloroethylene and compared themwith the stability of perchloroethylene without any stabilizer undersimilar conditions:

Acidity, Co or Wei ht Losses Milliliters, zMilligr ams) Percim" of 0 1 Nby Weight NaOH per co ihim im0 mini" 0ontion 62 8 2 Flask 23 9' denserfl-methoxypropionitrile 0. 01 6. 4 0. 6 8. 6 9. 4 Do 0.03 3.5 1.4 11.86.0 0. 1 2. 6 0. 8 3. 7 4. 5 0.01 4.4 0.5 7.7 3.7 0.03 2.5 1.2 8.3 6.7Do 0.1 6.2 0.6 5.1 3.4 No stabilizer (perchloroethylene alone) 2, 850. 08. 7 109. 5 179. 0 B-meth0xyacet0nitrile 0. 1 1. 3 7. 5 l3. 7

These tests show the improvement in stability of perchloroethylenecaused by the addition of an alkoxyalkylnitrile such as described above.Other halogenated aliphatic hydrocarbons containing up to 3 carbonatoms, such as carbon tetrachloride chloroform and trichloroethylene,may be stabilized in accordance with this invention by adding astabilizing amount of such an alkoxyalkylnitrile.

Although the present invention has been described with reference tospecific details of certain embodiments thereof, it is not intended thatsuch details shall be regarded as limitations upon the scope of theinvention except insofar as included in the accompanying claims.

This application is a continuation-in-part of our copending applicationSerial No. 167,258, now abandoned, filed June 9, 1950.

We claim:

1. The method of stabilizing perchloroethylene which comprises addingthereto a small stabilizing amount of an alkoxyalkylnitrilc having up to3 carbon atoms in the alkoxy group and up to 3 carbon atoms in the alkylgroup.

2. The method of stabilizing perchloroethylene which comprises addingthereto a small stabilizing amount of p-ethoxypropionitrile.

3. The method of stabilizing perchloroethylene which comprises addingthereto a small stabilizing amount of p-methoxypropionitrile. i

4. The method of stabilizing perchloroethylene which comprises addingthereto a small stabilizing amount of B-isopropoxypropionitrile.

5. The method of stabilizing perchloroethylene which comprises'addingthereto an alkoxyalkylnitrile in amount corresponding to 0.01 to 0.1 percent by weight of the mixture.

6. The method of stabilizing halogenated aliphatic hydrocarbonscontaining up to 3 carbon atoms which comprises adding thereto a smallstabilizing amount of an alkoxyalkylnitrile having up to 3 carbon atomsin the alkoxy group and up to 3 carbon atoms in the alkyl group.

7. A composition of matter comprising perchloroethylene and a smallstabilizing amount of. an alkoxyalkylnitrile having up to 3 carbon atomsin the alkoxy group and up to 3 carbon atoms in the alkyl group.

8. A composition of matter comprising perchloroethylone and a smallstabilizing amount of S-ethoxypropionitrile.

9. A composition of matter comprising perchloroethylene and a smallstabilizing amount of fl-methoxypropionitrile.

10. The method of stabilizing halogenated aliphatic hydrocarbonscontaining up to 3 carbon atoms which comprises adding thereto a smallstabilizing amount of an alkoxypropionitrile having up to 3 carbon atomsin the alkoxy group and having a boiling point below 200 C.

11. A composition of matter comprising a halogenated aliphatichydrocarbon containing up to 3 carbon atoms and a small stabilizingamount of a methoxyalkylnitrile having up to 3 carbon atoms in the alkylgroup.

12. A composition of matter comprising a halogenated aliphatichydrocarbon containing up to 3 carbon atoms and a small stabilizingamount of an ethoxyalkylnitrile having up to 3 carbon atoms in the alkylgroup.

References Cited in the file of this patent UNITED STATES PATENTS2,043,260 Missbach June 9, 1936 2,422,556 Klabunde June 17, 1947 FOREIGNPATENTS 512,458 Great Britain Sept. 15, 1939 620,296 Great Britain Mar.23, 1949

1. THE METHOD OF STABILIZING PERCHLOROETHYLENE WHICH COMPRISES ADDINGTHERETO A SMALL STABLIZING AMOUNT OF AN ALKOXYALKYLNITRILE HAVING UP TO3 CARBON ATOMS IN THE ALKOXY GROUP AND UP TO 3 CARBON ATOMS IN THE ALKYLGROUP.
 7. A COMPOSITION OF MATTER COMPRISING PERCHLOROETHYLENE AND ASMALL STABLIZING AMOUNT OF AN ALKOXYALKYLNITRILE HAVING UP TO 3 CARBONATOMS IN THE ALKOXY GROUP AND UP TO 3 CARBON ATOMS IN THE ALKYL GROUP.